This invention relates to the activation of alumina-bound porous crystalline silicate catalysts, e.g., zeolite catalysts, by contact with an aqueous ammonium solution under ammonia gas pressure such that a pH of at least about 8 is maintained in the solution. Zeolites deactivated by steam or hydrocarbon conversion processes are particularly suited to activation by the method of the present invention.
Methods for enhancing the catalytic activity of zeolitic materials are well known, including treatments involving ammonium ion or ammonia. U.S. Pat. No. 4,326,994 relates to a process for enhancing acidic activity of a highly siliceous zeolite by contact with steam and ammonia. Ammoniacal aluminum fluoride is taught as a reagent for zeolite activation in U.S. Pat. No. 4,427,788 while U.S. Pat. No. 3,684,738 discloses the treatment of deactivated oxygen regenerated zeolites with a source of hydrogen ions or hydrogen ion precursors such as an ammonium chloride solution. U.S. Pat. No. 4,427,788 teaches the use of aluminum fluoride in solution with at least one member selected from the group consisting of ammonium hydroxide and ammonia. U.S. Pat. No. 4,500,419 teaches zeolite activation by treatment with hydrogen fluoride, followed by ammonolysis. All of the above references are incorporated herein by reference.